Field of the Invention
Embodiments of the invention generally relate to sensors and, more particularly, to small form-factor pressure or temperature sensing assemblies, suitable for hydrocarbon production.
Description of the Related Art
Many industries and applications utilize sensors to measure parameters, such as pressure or temperature. In some cases, such sensors may utilize optical waveguides having a grating, such as a Bragg gratings or Fabry-Perot cavities, and the optical waveguides may have a characteristic wavelength reflectivity at a given pressure and/or temperature. As pressure and/or temperature change, the reflectivity characteristics of an optical waveguide may change in a predictable manner. Based on pressure and/or temperature-induced changes in the grating of a waveguide, a sensing device can determine changes in pressure and temperature by injecting a light pulse into an optical waveguide and measuring the reflected wavelength.
Such optical sensors may be used for sensing pressure and/or temperature in production tubing located in a wellbore completion for producing hydrocarbons. Traditional tubing strings, in which multiple lengths of tubing are coupled together, or coiled tubing may be deployed in the wellbore completion. In coiled tubing deployments, a length of tubing, which may be of a length appropriate for the depth of the completion, may be spooled onto a take-up reel. During installation, the tubing can be straightened and, using an injector head, can be run into the completion. Because coiled tubing is meant to be spooled onto and unspooled from a reel, the diameter of a coiled tube may be less than the diameter of traditional production tubing.
Several challenges exist with constructing optical sensors for use in production tubing, especially for coiled tubing deployments. One of these challenges involves the size of such sensors. While optical sensors for installation in traditional production tubing exist, various factors, including susceptibility of the glass fiber to damage and breakage due to its small size, flexibility, and brittle nature, make it difficult to build optical sensors for installation in more compact production tubing (e.g., coiled tubing deployments). For example, a conventional sensing gauge may be ¾″ in diameter and about 15″ long and may not fit within a coiled tubing.
There is a need, therefore, for a compact optical sensor assembly capable of operating in relatively high temperature and high pressure environments and deployable in various types of traditional and coiled production tubing.